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Leonard Nimoy

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Place a basketball in L.A. Place another basketball in NYC, then one in Berlin, Shanghai, and Capetown. Now, yank the Earth away and you have a nice scale model of a local cluster of stars (where the LA to NYC one is Earth to Alpha Centauri). Now, take a microscopic sand grain and shoot it in some random trajectory through that. The chances of it hitting one of the basketballs is about the same as the odds of ship hitting a star: effectively zero.

Good answer, better than what I( was going to say

Metryq wrote:

YellowSubmarine wrote:

Remember that question someone asked in here – does gravity work at the speed of light, or instantaneously? Well, you can't ever directly measure the answer unless the sun disappeared by magic.

Actually, it has been measured. Astronomer Tom Van Flandern measured the "aberration" (angle) between the Sun's light and its gravity. I made a few animations for him to explain astronomical concepts, and one of the animations was aberration. Another was an animated version of "what if the Sun magically disappeared?"

I'll be dumped on by all the Professional Physicists™ for saying this (they can't abide dissent), but we don't know what gravity is. In fact, we're no further ahead than Newton who did not explain gravity, he merely quantified it. And that's all we can do today. (Yeah, yeah, I know. Einstein and warped space, but all that does is shift the question of gravity, it does not explain it.) The answer is that gravity—whatever it is—is faster than light.

Maurice wrote:

The chances of it hitting one of the basketballs is about the same as the odds of ship hitting a star: effectively zero.

And if we look at the flip-side of that analogy, how do the starships so unerringly find the destination stars over such vast distances?

That's why they say, plot a course. Also, it's that big flamey thing over there. Addtional: in Australia we have a lot of Dutch shipwreckls off the coast of West Australia, simply because they didn't know it was there... until too late, obvously, the ships hitting reefs in the night, trying to keep the favourable trade winds as along as possible. Once they understood a bit more about navigation, they avoided it.

Timelord Victorious wrote:

Silvercrest wrote:

Metryq wrote:

And if we look at the flip-side of that analogy, how do the starships so unerringly find the destination stars over such vast distances?

Oh, that's easy. Just point the ship at the little dot and say, "Engage!"

When Captain Kirk said, "Second star to the right and straight on till morning", he wasn't quoting anything; he was giving specific course instructions.

They say "Course: 1765 Mark 5! Engage!" this will take you straight to Vulcan. Everyone knows that! And they can do it from memory at any relative position in space without consulting any kind of starcharts first.

This. Thiugh I woulld add I think real star charts would have to be 3D. In the Lensman series they had somethng called 'the Tank' which was used for navigation as well as plotting battle tactics.

__________________"… Times change, and so must I… we all change. When you think about it, we are all different people, all through our lives and that’s okay, that’s good! You've gotta keep moving, so long as you remember all the people that you used to be."

If these spaceships are going faster than the speed of light, then presumably they're moving faster than it would take them to see upcoming stars.

So how come they never run into one?

Warp speed is supposed to be like ftl right?

Light emitted from the stars in times past does NOT have to catch up with the ship. The photons are already there, traveling between the stars.
STL or FTL, the ship will have no problems seeing them.

Hmm, got caught up on the whole actual speed and what it would be like (where even at maximum warp you still technically wouldn't see the stars streak by. They would look as static as they do now, perhaps moving a slight tad, the way the moon might move as we cruise along a hwy in a car)

This is a good point though. Assuming that the stars in front of you would get blueshifted, and the ones behind you redshifted, does that mean that at FTL travel, the stars in front would blueshift beyond the visible spectrum? And the ones behind redshift out of visual wavelength range as well?

Um. I'm trying to decide if you're missing the sarcasm or playing along with it.

A little from column A, a little from column B...

__________________"… Times change, and so must I… we all change. When you think about it, we are all different people, all through our lives and that’s okay, that’s good! You've gotta keep moving, so long as you remember all the people that you used to be."

If these spaceships are going faster than the speed of light, then presumably they're moving faster than it would take them to see upcoming stars.

So how come they never run into one?

Warp speed is supposed to be like ftl right?

Light emitted from the stars in times past does NOT have to catch up with the ship. The photons are already there, traveling between the stars.
STL or FTL, the ship will have no problems seeing them.

But you do have to take into account a star's own motion through the galaxy, in accordance with its proper motion and radial velocity as viewed from Earth.

As you approach a star, you will be seeing it with light that was emitted from it at later and later times along its own trajectory. From your perspective, its position in space will therefore appear to shift as you approach it. Your journey to the star will have to take that into account so that you arrive where the star actually is, instead of where it was.

If you have no FTL sensors, an accurate assessment of the motion of the star is therefore essential. Hypothetical instantaneous FTL sensors would mitigate the problem of unknown factors, by locating the star where it actually is, so to speak, so that you can head directly there (as a good approximation for short travel times; or refined with proper/radial motion for a higher-order correction), which is generally speaking not where the light shows it to be.

__________________“A life is like a garden. Perfect moments can be had, but not preserved, except in memory. LLAP” — Leonard Nimoy (1931-2015)

If these spaceships are going faster than the speed of light, then presumably they're moving faster than it would take them to see upcoming stars.

So how come they never run into one?

Warp speed is supposed to be like ftl right?

Light emitted from the stars in times past does NOT have to catch up with the ship. The photons are already there, traveling between the stars.
STL or FTL, the ship will have no problems seeing them.

But you do have to take into account a star's own motion through the galaxy, in accordance with its proper motion and radial velocity as viewed from Earth.

As you approach a star, you will be seeing it with light that was emitted from it at later and later times along its own trajectory. From your perspective, its position in space will therefore appear to shift as you approach it. Your journey to the star will have to take that into account so that you arrive where the star actually is, instead of where it was.

If you have no FTL sensors, an accurate assessment of the motion of the star is therefore essential. Hypothetical instantaneous FTL sensors would mitigate the problem of unknown factors, by locating the star where it actually is, so to speak, so that you can head directly there (as a good approximation for short travel times; or refined with proper/radial motion for a higher-order correction), which is generally speaking not where the light shows it to be.

So - you can either use FTL sensors (even more 'magic' than FTL travel) to see the star or you can calculate the stars' current position by using models we know today.
If you must 'see' where a star is NOW, you can always use its gravitational or electrostatic field to detect it (you need insanely accurate sensors for this, though).

As for 'unknown factors', if at your destination there is something that can substantially alter the trajectory of a star so fast, you're better off mistaking your course.

The challenge is how to get to the stars, not how to determine their position at any given time.

Well, the sun is moving around the galaxy at about 500,000 miles per hour, which sounds like a lot, but it isn't when compared to any FTL travel. At twice the speed of light you'd only have to lead the sun's position by an arc-minute, which means that for some random star that doesn't have a crazy velocity, to hit it you'd have had to been aiming at it from the start with the same accuracy you'd have with a modern off-the-shelf scoped hunting rifle.